This project is fundamentally concerned with the relationship between the activity of retinal amacrine cells and an extracellular potential, the proximal negative response (PNR). Conventional electrophysiological techniques for recording intra- and extracellular light-evoked potentials will be employed, together with response averaging techniques. The retina of the mudpuppy will be used as it now affords a singularly unique opportunity to pursue the following specific aims: (1) to determine the relationship between intracellularly recorded amacrine cell activity and the PNR; (2) to quantitatively study stimulus related properties of amacrine cell responses and the PNR; (3) to further define the feasibility of investigating the PNR and hence proximal retinal function through conventional ERG recording techniques; (4) to attempt to describe the mode of synaptic interaction between amacrine and ganglion cells and attempt to establish some preliminary evidence regarding amacrine-amacrine or bipolar- amacrine interactions. It is expected that these basic observations would aid in establishing the interpretative validity of the PNR, thereby permitting it to be used as a tool for the analysis of proximal retinal mechanisms in other species, including man.